eso9110 — Science Release

A Ground-based Image of Minor Planet (951) Gaspra

Galileo Fly-By on October 29, 1991

29 October 1991

This is a ground-based photo of the first minor planet ever to be visited by a spacecraft. On October 29, 1991, the NASA spacecraft Galileo will pass minor planet no. 951 Gaspra on its way to Jupiter where it will arrive in December 1995. The distance from Gaspra to the Earth will be 410 million km at the time of the fly-by.

Gaspra was discovered on July 30, 1916 at the Simeis observatory in the mountains of Crimea, then Russia. The discoverer was the well-known Russian astronomer Grigorij Nikolaevich Neujmin(born 1886 in Tbilisi, Georgia; died 1946 in Leningrad), who later became Director of that observatory (1925 - 1931 and 1936 - 1941) and Director of the Pulkovo Observatory near St. Peterburg (1944 - 1946). During three decades he discovered 72 minor planets and 6 comets.

Neujmin's dedication for (951) Gaspra reads as follows: "Named after the resort on the southern coast of Crimea, in which the famous Russian writer Lev Nikolaevich Tolstoy (1828 - 1910) spentmany years of his life." The village of Gaspra is located about 10 km south-west of Yalta.

The present photo was obtained with the 1-metre ESO Schmidt telescope at La Silla on April 9, 1991 and served to measure an accurate position of Gaspra, in support of the navigation of Galileo.The exposure lasted 10 minutes and Gaspra is indicated with an arrow. On this date, its distance from the Earth was 262 million km and the magnitude was about 15. Gaspra measures about 13 km across, too small to be seen as more than a point of light on this photo.

The background of the photo is a region in the southern constellation Ophiuchus (the Serpentholder) which is characterized by relatively few stars, but many bright and dark nebulae. The brightest of the three stars in the top right corner is the 5th-magnitude Rho Ophiuchi, a hot and young double star. It is surrounded by nebulosity that reflects the light from the stars.